In the past years the development of VC was discovered to be actively regulated and as being influenced by inhibitors of calcification (e.g. matrix-Gla-protein, fetuin-A). Matrix Gla protein (MGP) is a powerful vascular wall-based inhibitor of VC. MGP is produced by vascular smooth muscle cells and needs post-translational modification by vitamin K dependent gamma-carboxylation to be fully active. The role of MGP was discovered in knock-out mice, which died from rupture of a massively calcified aorta. Functional vitamin K deficiency induced by administration of warfarin leads to the development of VC, which in turn can be inhibited by subsequent administration of vitamin K1. Warfarin inhibits the vitamin K mediated gamma-carboxylation, which leads to the production of noncarboxylated and inactive MGP (ucMGP).